Out past 450-500yds I will take a 6mm ARC AR with a 18" medium profile barrel and variable optic to match. IMHO, the 6mm ARC checks the most boxes, barrel life at around 52,000 psi being just one of them. I really think it is the future and time will tell.
- Thread starter BP 3papa 7sierra
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Yes, no and maybe not and or......! You don't always get to keep your cake and eat it as the saying goes. There are trade off's with some of this stuff.
I haven't read every single post so here are some quick thoughts for you all.
Barrel length although I do agree but I will say at times and it depends on the cartridge it can effect accuracy. Most of the time I'll say it's not as critical but it can and will have an effect.
Twist rate normally doesn't effect velocity but it can have an effect on bullet failure as well as accuracy. Take a poor quality bullet and spin it too fast and it can have a negative impact on accuracy but the bullet might not even fail etc...good example as we are talking 5.56 stuff here. I've seen production quality barrels in 1-7 twist and 55gr ball ammo key hole the bullet on the target at 100 yards. Same gun and load up 52gr match bullets and no bullets go thru the target sideways and would hold 3/4moa groups at the same velocity spec as the ball ammo.
Upper 200k rpm on bullets and the hard line in the sand is 300k rpm....bullets will start coming apart. Your on borrowed time. The problem can be amplified by a poorer quality barrel with a rough bore or a rough throat from the chamber work or as the barrel starts to get higher round counts on it...the throat will get rougher and the bullet is going to take more of a beating and the really high twist rates will not be helping you at all.
Most calibers when you look at loading manuals or what the ammo is rated at for velocity on the ammo boxes is produced with 24" barrels. I'll say 95% of them. Some exceptions are 300AAC is a 16" barrel, 30 Carbine is a 20" barrel, some of the Weatherby's but not all might be in 26" barrel etc...
6ARC the industry standard is 24". Same as 22RF it's 24".
Also when you guys are comparing stuff....take what you read with a grain of salt when one guy says I get 3000fps with my 300WM in a 24" barrel but you say I can only get 2800fps with the same bullet and same load etc....unless you know if the same chamber was spec was used for each gun...that is one variable. Also unless you know the actual bore and groove size to the 4th decimal place....you are also not comparing apples and apples. I've seen where the throat of the reamer cut the freebore diameter .0001" undersize and pressure went up 6k psi and velocity went up with it. So unless you know all the details...you are not comparing apples and apples.
I'm involved with some testing with coatings/treatments of barrels right now. A pressure barrel got treated/coated....the treatment process isn't suppose to change the bore size but it did. We had the barrel +.0003" over min spec. but with in the max tolerance of +.0005". The treatment process basically made the barrel .0004" tighter and in this case took the bore .0001" undersize and the groove size right to .0000". The same ammo in a spec. barrel is giving 2700fps and pressure is under the max Saami for the cartridge. Run the same ammo in the tight/min spec. test barrel and pressure is jumping almost 10kpsi and velocity is up 100fps+.
Later, Frank
Bartlein Barrels
I haven't read every single post so here are some quick thoughts for you all.
Barrel length although I do agree but I will say at times and it depends on the cartridge it can effect accuracy. Most of the time I'll say it's not as critical but it can and will have an effect.
Twist rate normally doesn't effect velocity but it can have an effect on bullet failure as well as accuracy. Take a poor quality bullet and spin it too fast and it can have a negative impact on accuracy but the bullet might not even fail etc...good example as we are talking 5.56 stuff here. I've seen production quality barrels in 1-7 twist and 55gr ball ammo key hole the bullet on the target at 100 yards. Same gun and load up 52gr match bullets and no bullets go thru the target sideways and would hold 3/4moa groups at the same velocity spec as the ball ammo.
Upper 200k rpm on bullets and the hard line in the sand is 300k rpm....bullets will start coming apart. Your on borrowed time. The problem can be amplified by a poorer quality barrel with a rough bore or a rough throat from the chamber work or as the barrel starts to get higher round counts on it...the throat will get rougher and the bullet is going to take more of a beating and the really high twist rates will not be helping you at all.
Most calibers when you look at loading manuals or what the ammo is rated at for velocity on the ammo boxes is produced with 24" barrels. I'll say 95% of them. Some exceptions are 300AAC is a 16" barrel, 30 Carbine is a 20" barrel, some of the Weatherby's but not all might be in 26" barrel etc...
6ARC the industry standard is 24". Same as 22RF it's 24".
Also when you guys are comparing stuff....take what you read with a grain of salt when one guy says I get 3000fps with my 300WM in a 24" barrel but you say I can only get 2800fps with the same bullet and same load etc....unless you know if the same chamber was spec was used for each gun...that is one variable. Also unless you know the actual bore and groove size to the 4th decimal place....you are also not comparing apples and apples. I've seen where the throat of the reamer cut the freebore diameter .0001" undersize and pressure went up 6k psi and velocity went up with it. So unless you know all the details...you are not comparing apples and apples.
I'm involved with some testing with coatings/treatments of barrels right now. A pressure barrel got treated/coated....the treatment process isn't suppose to change the bore size but it did. We had the barrel +.0003" over min spec. but with in the max tolerance of +.0005". The treatment process basically made the barrel .0004" tighter and in this case took the bore .0001" undersize and the groove size right to .0000". The same ammo in a spec. barrel is giving 2700fps and pressure is under the max Saami for the cartridge. Run the same ammo in the tight/min spec. test barrel and pressure is jumping almost 10kpsi and velocity is up 100fps+.
Later, Frank
Bartlein Barrels
for taking a heart beat i'm going 18" rifle length gas tube 7" twist with a 77gr tmk. preferably black hills loaded
Original question was is 14.5 too short for DMR use. No - it is fine.
I tend to use 14.5 barrels w/ 1:7 (but own from 10.5 to 20). Lots of variables in performance to consider.
An active unit DMR might well be using the heavy but truly awesome HK M110A1 today with its .308 goodness!
I tend to use 14.5 barrels w/ 1:7 (but own from 10.5 to 20). Lots of variables in performance to consider.
An active unit DMR might well be using the heavy but truly awesome HK M110A1 today with its .308 goodness!
For the OP, the 14.5" 5.56 is the tool you have to work with. I would prefer a larger caliber SBR . As stated above, DMR is not defined by the "R"ifle placed in the hands of a DM. From my inventory I would choose the a short 6.8 SPC II or KAC SR-25 14.5" ACC; anything outside their effective range, get on the radio and call in air support. Some suggestions just for fun that I would select over 5.56 all day long.
What ammo does your 6.8 prefer?
When I took my 12” Grendel out at 800yds the first time, using Federal 120gr OTM (not the highest BC bullet in that weight class by a long shot), with a 1-4x LPVO using the magazine as a monopod, I was 9/10 on a 2’x3’ steel buffalo at 800.
My little son was sitting on the tailgate watching, and every time he heard impact, he would say, “Ting, ting, ting.” It was his first time out with me shooting steel. I was thinking, “You haven’t seen anything yet."
That was at 6600ft elevation, so the air is quite thin, but I just didn’t see a huge difference between it and a 16” or 18” Grendel from shooter’s perspective. I can show you in numbers exactly how different it is, but the numbers are so minute looking through the scope and just connecting that it didn’t matter, especially with a tree reticle.
A 10.5” Grendel has more muzzle energy than a 20” 5.56, and only gets better from thereon-out, so it isn’t hype or reliant on 24” pipes to get a lot done.
Last I looked, defense wasn’t even in the top 20 high revenue industries in the US.
Most of what is said about politicians and defense kick-backs is outhouse lawyer hearsay, with no real examples, especially for small arms.
There are scores of US Army programs of record right now with billions in funding, and they aren’t even remotely down in the small arms money. Aviation, Armor, Long Range Fires, Artillery, Comms, Net-Centric, Medical, UAS, new trucks, etc. are far bigger budgeted line items.
Politicians’ panties get tight when Pharma, energy, Wal-Mart, Big Tech, Banking, Insurance, Investment Funds, Teacher’s Union Retirement Accounts, and things like that pay for their campaigns and “information retreats”, not defense. Defense is low-ball pennies.
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